The Harvard Medical School-based research training program entitled "Infectious Diseases and Basic Microbiological Mechanisms" offers a minimum of 2 years of laboratory-based research training for physicians and postdoctoral Ph.D. scientists. The aim is to provide substantive research training experience with relevant supporting course work and thereby to enable the postdoctoral trainee to become an independent investigator in the fields of infectious diseases and microbiology. Training laboratories are available in eight major areas (1) virology, (2) bacteriology, (3) parasitology, (4) immunology, (5) molecular biology and genetics, (6) cell biology, (7) epidemiology, and (8) biochemistry. The purpose of this renewal application is the continuation of this highly successful program, which has been supported by the NIH for the past 25 years During the past 5-year period, approximately 176 trainees completed the program. Of these individuals, 131 now hold university faculty positions or work in government service. An additional 37 have taken positions as scientists in industry. Although only eight positions per year are supported by this grant, 175 postdoctoral trainees are currently being funded by our training program in the laboratories of the 39 participating research mentors.